The main objectives of these studies are (i) to identify and characterize all proteins that are specified by the defective human parvoviruses (AAV) and to determine similarities and differences with autonomous parvovirus proteins, (ii) to define the mechanism(s) by which the AAV proteins arise and (iii) to define specific functions of the AAV proteins. We have now found several AAV structural protein species previously not known to exist. Post-translational processing does not appear to account for production of any AAV structural proteins, although they share large proportions of sequences-in common. The mechanism that regulates translation of AAV proteins is of fundamental interest and is now being investigated. Among methods used are affinity chromatography, gel electrophoresis, in vitro translation of viral RNA and protease digestion analysis.